Built-up vertical zinc retort



Aug. 14, 1928. I

I,68O, 726 F. G. BREYER ET AL BUILT-UP VERTICAL ZINC RETORT' Filed March 5, 1927 2 Sheets-Sheet 1 ATTORNEY8 I 'l,680,7 26` F. G. BREYER ET AL BUILT-UP VERTICAL ZINC RETORT Filed March 1927 2 Sheets- Sheet- 2. 4

%TE 4, W

ATTORNEYS Pa tented A g. 14, 1 928.

UNITED STATE'S- I V 1,68o'7z .PATENT OFFICE.,

FRANK e. BREYER AND EARL H. BUNCE, or PALMERTON, PENNSYLVANIA, uAssIGNons' TO THE NEW JERSEY ZINC COMPANY, NEW JERSEY.

Application filed March 5,

This invention relates to externally heated Vertical retorts or reducing cham-bers for smelting or reducing zineiferous materials, and has for its object the provision of 'an improved retort or reducng chamber of this character.

At the present time, all commercial zine reducing chambers or retorts (extemally heated) are. true monoliths, with but a single opening for introducng the charge, withdrawng the residues and exitingthe -zinc-' hearing gaseous products. This opening during the active reduction period is completely filled and closed from the atmosphere by a condenser (and its luting) for the metallic zine vapor. These monoliths are made by ramming plastic heat refractory or'temperature resistant material into suitable molds or by iextruding such material under pressure. The resulting plastic Vessels are most carefully dried and burned, and if the slightest crack appears are rejected as unfit to be placed in the heating chamber or laboratory of the zinc or spelter furnaee. The primary reason for' making these retorts true monoliths and with but one opening is the full realization that the slightest leakage of heating gases into the retort is fatal to good condensation to Zinc metal of the zine vapor evolved in the retort.

XVith small retorts of the size now commonly used in commercialspelter furnaces (6 to 9 inches internal diameter and about 4: to 5 feet long), the disadvantages of constructing the retorts as true monoliths are not of particular importance. With reducing chanibers of substantially greater capacity, such as contemplated in the improved method of zinc srnelting` described in our copendiug patent application, Serial No. 163.902, filed January 27, 1927, the disad- Vantages of the true monolith Construction become so great as to render this manner of making the reducing chamber commercially mpracticable. consequently, in the construction of reducing chambers of relatively large reducng Capacity built-up structures become a practical necessity. By built-up structures wemean structures that are not molded, formed or cast as one piece from fluid or plastic base material, thereby forming a monolith, but on the contrary, are built up into the required size and shape by fitting together a number of pieces or shapes of solid material which are bonded OF NEW YORK, N. 2.; A

Burma-Ur VERTICAL znic'nnrom'.

1927. Serial No. 172,951.

together by some form of cement or joint filler. The znc metallurgist, however, is not' inchned to regard built-up reducing chambers with any favor, no doubt because of the many fruitless .attempts toreduce znciferous material in built-up mumes. Even n the Very early days of zine smeltmg bult-up mufiles were proposed and tried, but these built-up structures invariably gave such poor recoveries of zinc and such poor condensaton to zine metal that they were all abandoned in favor of the small truly monolthic` retort that-has become standard practice in zmc smelting for making ziuc metal. i

In View of the use of built-up mumes in other 4 ndustries and arts, it perhaps requires some explanation to understand why a built-up mufile has not heretofore proven satisfactow n the art of zine snelting In other industr1es, where built-up mufiles are used under condtons of high temperature, small leaks into or out of the mufile are not of serious consequence In the case of zinc smelting in the reducing chambers or retorts of the prior art, however, the smallest leak into' the reducng chamber or muflle has proven fatal to the good condensation of the zin va or evolved. This seems to be true even wl ien there is some slightly greater pressure inside of the mufle than outside, since diffuson of oxygen into the muftle against the' pressure therein appears to be of sufiicient magntude to bring about the harmful efi`ect. In the early attempts to use built-up mufiies for zine smelting other difliculties were encountered due to slagging out or breaking of the bonds or j oints, thereby causing Cracks when the mufile-cleaning tools were used.

The principal difl'culty, however, in the* former attempts to use built-up muifies in zine smelting was due to the factthat the muflies were invariably' tied in, supported by or their arches Sprung from the furnace or laboratory lining in numerous places. WVith the temperature of the muffle walls going from blackness when a fresh char-go was put into the muffle up to 1200130 1400 charge was worked-ofl", and these temperature changes repeated with every oharge, the wall of the mufile contracted and expanded difierentially with respect to the CORPORATION or `C., and often higher, before the last of the i laboratory or furnace walls to which it Was tied in and ruptures and cracks on the mufiie inevitably took place in conseguence thereof. We have discovered that i the muflle or retort is built u so that it is supported and tied in to the la oratory or furnace lining at only one lace (preferably its base) and due regard ta en of other factors, a built-up retort can be made sufl'ciently tight for good condensation of the zinc vapor evolved. We have further found that not only is it imortant that the 'reducing chamber or retort Be not tied in at anyother place than at its base, but that the shape of the individual units or pieces which fitted to ether make up the retort be such as to ma e each unt or piece capable of expansion and contraction without throwing any strain upon the neighborng units or pieces. We have also found that it is highly advantageous that each piece in the built-up retort be of such shape and size that it may be densely ressed, uniformly dried and burned, and be ?ree of internal strain, which in eflect calls for the use of the smallest pieces practicable. Moreover, since the retort is to be supported and tied into the furnace structure at only one place, the disposition of the retort in a vertical position becomes essential, and a cylindrical retort highly advantageous', because under such conditions the retort may be appropriately supported at its lower end with suflicient thickness of wall to carry the weight of the entire retort without bending or wabbling, and because a cylinder exhibits the least harmful effects of heating strains when it is repeatedly heated up and cooled down.

Our present invention accordingly contemplates the provision of an externally heated and vertically disposed reducing chamber for zinciferous material built up of a multiplicity of units or pieces of temperature-resstant material bonded'together horizontally or vertically and horizontally into a substantially zinc-vapor-tight chamber supported and tied in at its lower end only. The individual temperature-resistant units or pieces are preferably annular, or cylindrical, or standard brick shapes such as circle, ke cupola, ring section or kiln.

- ese units or pieces are moreover of such sha e as to permit independent expansion an contraction of each unit or piece without thereby imparting any objectionable strain to adjacent units or pieces. To this end, it is our preferred practice to provide substantially plain butt joints between adjacent units or pieces. To minimize expansion and contraction, it is desirable that the temperature-resistant units or pieces be made of temperature-resistant material having a relatively low temperature coeflicient of expansion, and since the reducing chamber is externally heated, the temperature-resistant material should referably have good heat conductivity. S con carbide or carborundum, aluminum oxide, ziroonium oxide and zirconium silicate are satisfactory materials for this purpose. The individual temperature-resistant pieces are extruded or machine-pressed under pressure to give hh density and are dried and hardened (fire under conditions adapted to minimize the strains remaining therein or 'likely to develop in the heating up of the chamber or retort they o to make up.

The rincples of the invention and their practicfl application to the Construction of reducin chambers for zine smelting will be best understood from the following description taken in 'conjunction with the accompanying drawings in which Fig. 1 is a sectional elevation of a zine reducing or smelting-furnace embodying the novel built-up reducing chamber of the invention, j

Fig. 2 is a section of the furnace shown in Fig. 1 on the section line 2-2,

Fig. 3 is a combined sectional elevation and cross-section of a modified Construction ofdbuilt-up retort embodying the invention, an

Fig. 4 is a combined sectional elevation and cross-section of another modified form of the invention.

Referring to Figs. 1 and 2 of the drawings, the built-up retort 10, embodying the prmciples of the invention, is surrounded by a heating chamber or laboratory 11. The heating chamber 11 is built within a furnace structure comprising an outer steel shell or casng 12, a layer of Sil-o-cel powder 13, an intermediate lining 14 of one or more layers of fire brick or other appropriate material and an inner lining 15 of heat-refractory or temperature resistant material such, for example, as Carbofrax brick. Appropriate openings are provided through the wall of the furnace structure permittin the insertion of pyrometers 16 wthin the eating chamber 11 for ascertaining and appropriately controlling the temperature throughout the length of this chamber.

The furnace illustrated in the drawings is heated by the hot roducts of combustion from burning gas, alt ough it is to be understood that any appropriate means may be employed for heating the reducing chamber or retort 10. The fuel gas is supplied from a gas main 17 to a plurality of vertical passages of conduits 18 arran ed within a recuperator 19 built within t e furnace structure alongside of the heating chamber 11. Similarly, air is supplied' from a main 20 to a plurality of passages or conduits 21 in the recuperator. The passages 18 and 21 are rovided in a plurality of spaced vertical wal 22 built up of temperature-resistant brick, tile or the like. It will be understood, of course that the lining of the recuperator may be built of less temperature-resistant material than the lining of the heating chamr ber 11, and that the recuperator will be provided with appropriate clean-out openngs for the various gas passages thereof. v From the top of the recuperator the preheatedfuel gas and air are delivered from their respective passages 18 and 21 toan appropriate mixer and bur-ner (not specifically shown) near the top of the heating chamber 11. The resulting hot products of combustion pass downwardly around the retort 10 to an outlet 23 near the bottom of the heating chamber 11,. and thence upwardly 'through a. vertical flue 24 to the top of the recuperator. The recuperator is provided with staggered horizontal baflies 25 which cause the heating -gases to follow a Zig-Zag path in their flow through the recuperator to the gas outlet 26 and stack 27.

The furnace structure of the heating chamber 11 is mounted on a metal base plate 28 supported on an appropriate 'oundation 29 of concrete or the like. The base plate 28 supports the built-up retort 10 and has a central opening directly beneath and of the same dimensione as the interior. crosssection of the retort A metal cylinder 30 is bolted, or otherwise appropriately secured, to the underside of the base plate 28 and serves as an extension of the retort 10` below thebase-plate. A rotating table 31 is mounted directly beneath and approprimeans of removal not ately spaced from the bottom of the cylinder 30 and serves to support the charge' in the retort 10 and, by its rotation in conjunction with a plow orscraper, permits the` dscharge of spent residues from the bottom of the 'retort as desired. From the rotating table 31 the spent residues are delivered to a conveyor or other appropriate shown in t e drawings.

The built-up retort 10 is supported exclusively at the base and is at no other place throughout its length attached to or otherwise tied into the heating chamber or furnace structure;` The upper end of the retort extends freely through the top of the furnace structure. A cylindrical metal casting 32, preferably a nickel-chromium iron alloy such as Hybnickel, rests on top of the retort. A ring of ordinary fire brick 33 is preferably interposed between the top Carbot'rax ring of the retort and the cylinder 32, in order to keep the Carbofrax brick from contact with the metal. The cylinder 32 is surrounded by a layer of hardened carbon paste 34 encasedvby sheet metal 35, which in turn is surrounded by a mass of dust coal 36 confined by a sheet metal wall 37..

This dust coal also provides a mobile seal between the retort and the opening in the topof the urnace structure through which the retort extends. The metal cylinder 32 with its surrounding layer of hardened carbon paste 34: thus rest on top of the retort 10 and are free to move therewith, and

at the same time the top ofthe retort is effectively sealed. It will thus be seen that the retort 10 is supported entirely at its base or bottom and is at no other place secured to or tied into the furnacestructure, and is therefore free to expand or contract as it will.

The metal cylinder 32 has a lateral gas outlet 38 lined' with a graphite tube 39 leading to an appropriate condenser, preferably of the type described in the patent application of Frank G. Breyer, Serial No. 167,135, filed FebruarylO, 1927 but not illustrated in the ac'companying drawings. The top of the cylinder 32 is provided with a charging device comprising an inverted sheet metal funnel 40 appropriately mounted within the cylinder and a movable plug or bell 41. The space between the umel 40 and the cylinder 32 is filled with darkened' carbon paste 42 and an overlaying mass of dust coal 43, in which the rim or edge of a cover 44 is embedded.

Where the gas ofitake (38-39) of the retort operati ely enters or abuts on the condenser or any other appurtenance, which is relatively fixed with respect to the expanding or contracting movements of the retort, it is important that the connection be adjustable to permit such 'relative movements. Or, if desired this connection may be made and broken after the retort is up to heat and before it is Gooled down, respectively. The condenser or other -appurtenance to which-the gas ofl take of the retort is operatively connected may be adjustable `as to height, and then raised or lowered as the expanding or contracting retort wall raises or lowers the gas offtake.

The retort 10 is built up of a multiplicity of superposed annularnnits 10' of appropriate temperature-resistant material. In the furnace illustrated in the drawings, the retort 10 is 4:0 feet long or tall and 2 feet internal diameter and has a wall thickness of 4 inches. The dimensions of each annular element or unit 10' are 24 inches inside diameter, 33 inches outside diameter, 4 inches wall thiclme'ss and 2 inches high.

The annular units 10' are preferably made of silicon carbide (or carborundum) grain accurately sized and preferably shaped by extrusion under pressure to give the maximum density. The annular units are given two firings, the second at a higher temperature than the units'are expected to attain in use, wth the idea of relieving all strains and bringing out any faults, so that imperfect units may be discarded.

The retort 10 is built up from the baseby laying: these a'nnular units one upon another. The joints between the superposed units are filled with Carbofrax cement and the units are pressed or' hammered down into place with joints of preferably one-eighth inch or less. As the 'ont filler or cement we preferably use Carhofrax No. 4 cement, consisting principally of sized carborundum and a small amount of glutrim binder or dried sulfite li nor and a small amount of cla By the addition of water, the cement is ma e just plastic enough to flow under pressure, but is made suflicie ntly dense to leave a real body of carborundum in the joint when the water of the cement eva orates. The retort 10 may in this manner e built up great heights provided it is not tied in with any furnace wall or kicker which would interfere with its free and uniform expansion as it heats up. The low temperature coefiicient of expansion of Carbofrax brick is of particular advantage in constructing such large retorts.

The retort 10 illustrated in Fig. 3 is built up in substantially the same manner as the retort 10 of Figs. 1 and 2. The individual pieces 10' with which the retort 10 is bult up, while annular units, are perhaps more aptly described as cylndrcal elements or units. Thedimensions of the retort itself are substantially the same as the retort 10, and the cylindrical units 10^' are 6 inches in height and have a wall thckness of approximately 3 inches. v

Where the retort is built up of integral cylindrical or annular units, as distinguished from units assembled from brick or small shapes, we prefer that the height or verticaldimension of these units should not exceed about 6 inches, in order that the advantages of our improved built-up Construction may be realized to the fullest degree. On the other hand, we have successfully operated for many months a cylindrical verteal retort 25 feet in height and built up in accordance with our mvention of cylindreal units 18 inches in height.

The retort 10 illustrated in Fig. 4 is bult up of brick 10 preliminarily asembled in the annular units 10 The br ck 10 are Carbofrax circle brick of the following ap roximate dimensions: 9 inches by 6 inc es by 4 inches by 2 inches. welve of these circle brick are used n making up each annular unit 10 The dimensions of the annular units are: 24 inches inside diameter, 33 inches outside diameter, 4 inches wall thickness and 2 inches high.

The circle brick 10 are preferably made of silicon carbide, or carborundum, gram accurately sized and further machinepressed to give the manimum density. Thebrick are given twofirngs for the reasons hereinbefore mentioned. Such brick run remarkabl true to shape and size after the' double firng. Nevertheless, it s our preferred practice to treat these brick on a revolving send grindng table where all irfaults eovered over by the surface regularities are eliminated, the Contacting surfaces of the brick cut smooth and any laze revealed and the fault brick rejecte.

After the smoothing and uniforming operation on the revolvingsand table, the brick are sorted to sizes within one-sixtyfourth of an inch on the vertical or 2 inch dimension. Twelve of these circle brick are then laid in a ring upon a plane surface and the vertical joints filled in with Carbofrax Now& cement. By the addition of water, the cement is made 'ust plastic enough to flow under pressure, ut is made sufliciently dense to leave a real body of carborundum in the joint when the water of the cement evaporates. The vertical joints between adjacent brick in the ring are made up with an initial thickness of inch or' more of cement. Two or three heavy iron wires are next laeed around the assembled ring of circle brick and the ends of the wires twisted together so as to exejt a very powerful contracting and compressing force. Under such treatment the vertical joint be- {ween adjacent brick is reduced to inch or ess.

The retort 10 is now built up from the base by laying these rin s of circle brick one upon another. In this o eration the rings are handled as units, the rick in each ring or unit'being tightly held together by the encircling wires. The horizontal joints between the superposedrings are filled with Carbofrax cement and the rings a're hammered down into place with joints of inch or less. The horizontal joints between the superposed rings, being at all times under compression in consequence of the weight of the superposed rings, need not be so carefully made as the vertical joints between individual circle brick in each ring, which latter joints are under less compressive strain after the encircling wires are removed. The encircling wires are removed when some four or five feet of the retort structure has been built thereabove, the weight of the su erposed structure being then sufiicient to cep the lower individual circle brick in position. In this manner, the retort 10 may be built up to great heights, provided it is not tied in with any furnace wall or kicker which would interfere with its free and uniform expansion as it heats up.

While in our preferred practice the filling material, cement or bond in the -joints between the annular or cylindrical units or the individual brick or pieces may harden and solidify when cold so as to be a true bond between the pieces, stronger in some cases than the pieces themselves, thiscondition of the cold strength of the fillin material is not essential. The function o the filling material in the joints is to furnish a filler for the cracks which would otherwise be present,

'with a minimum number of 'oints.

and to make the joints sufl'ciently dense to be substantially non-porous to zine vapor. The filler in the joints must moreover have the Capacity of not fusing away at the elevated temperatures to which the reducing chamber is subjected, but must stay in position in-the joints. It is for these reasons, among others, that we particularly specify that the fillin or bonding material be' made up with as high apercentage of solids and as small a percentage of water or other slip promoting material as possible. This preference for a dense filling material makes thin uniform joints more diflicult of attainment, particularly in the vertical joints, but our improved method of assembling the pieces overcomes' this` handicap and makes possible zinc-vapor-tight joints. When, therefore, we speak of the pieces being bonded? together we mean that the joints, both horizontal andvertical, are so filled as to be substantially zinc-vapor-tightaunder Operating conditions. e

It is to be understood that the reducing chamber 'may be of any desired sectional configuration. While we have herein s oken of the units 10', 10 'and 10 as "cyhndrical or annular" in shape, we have used these words withoutrestriction as to the exact configuration of' the units. In general, we pre-fer these units to be of circular section, but it is to be understood that the units may be elliptical, oval or of any other appropriate sectional configuration.

-It has heretofore been considered desirable to construct built-up muflles or reitorts s a result of our investigations an experiments we have found that this does not hold for a built-up verticalzinc retort. Thus, we have found that the number of joints in a builtup vertical zinc retort may with advantage be increased to the number required by standard machine-pressed brick shapes, more particularly where, as in our present invention, the reducing chamber or retort is supported only t its base and not otherwise tied into the rnace structure.

As hereinbefore stated, we have found that the-individual units or pieces which fitted together make up the retort be of such shape as to make each unit or piece capable of expansion and contraction without throwing any strain upon the neighboring units or pieces. p u

In our early experiments, we built up the vertical retort with Carbofrax cylindrical units or sections having bell and spigot joints such as commonly used 'for joining pipe lengths of various kinds. These sections were 18 inches long or high, 15 inches internal diameter with a wall thickness of about 2 inches. In the operation of this built-up retort, the bell and spigot joint not only proved of no advantage but a positive and very serious disadvanta e; and this in spit'e of the fact that Carbo rax Ware is unusually strong for non-metallic temperature-resistant material, and moreover has'a very low temperature coeflicient of expansiot This retort failed by the cracking and falling out of a big piece of the retort wall as a consequence of putting cold charge into the upper end of the retort when' the latter was at a temperature around` 1200 C. When the assembly was inspected after cooling down, a number of cracks were found in the retort in addition to the several which werethe direct and principal cause of the failure. In every case, these cracks started' or ran away from either the bell or spigot ends and generally extended from one spigot end into the bell end of the next lower unit or section. The evidence was unmistakably clear that the sections were unusually liable to start cracking from the bell end and that if a crack ran down a section to the spigot end it was almost certain to crack the bell of the unit below because of the confinement of the spigot within the bell of the next lower unit.

It required consider-able courage 'on our part to take off the bell end of the units thereby leaving them true sections of cylinders with no tie-in from one section to another, other than the plastic bond between the joints. The units or sections were then of the formkillustrated in Figs. 1, 2 and 3 of the accompanying drawings. Such units can not only be made and burned with considerably less strains remaining in them, but, assembled and in operation can expand irregularly with respect to one another. That is to say, if one unit in the heating up tends' to expand elliptically or eggwise on one axis and another unit tends to do the same thing on another axis, they may do so without one unit throwing a strain upon another unit. Under these circumstances, the flow or movement 'takes lace in the plstic cement or joint filler. hese true cylindrical or annular units gave very superior service 'to that obtained with the bell and spigot runits. i

Pursuing the same line of reasoning, but assuming that'even the best of such sections or units may crack, the question of keeping the cracked piece from falling out and ab'- solutely ruining the entire retort leads to the units are say 4 thick and only 2 which we have ing out. Take the case where the annular' 25 high. If such an annular unit develops two 4 Cracks from. the to to the bottom, that is, through the 2%" dimension, the loose piece would not fall out even if there were no cement bond in the joints because the loose iece is held as a flat layer with a 4 of hearing surface on its upperand lower sides.

It is accordingly our preferred practice to go torin or' assembled rings made up of circle bric or other standard ring-forming shapes which are of relatively low vertical height and preferably of less vertical height than the ring width or wall thickness. In making a temperature-resistant 'ring from a plastic base, it is always possible to make and burn a flatrring better than a square one or one of greater height as compared with its wall thickness.

As a last precaution to insure as good a built-up retort as possible, from the standpoint of absence of residual.- strain which might later develop Cracks n o eraton, these annular units may be heate up and very suddenly cooled to make the residual strains crack the unit exactly as they would in operation. The cracked unit which has a material tendency to open outward may then have the thin cracks filled with cement which when burned with the unit in final position constitutes a zinc-vapor-tight jont. Or, if desired, the annular umts may be mechanically broken instead' of cracked by heat strains, and the cracks filled with cement. The last step in this direction is to construct the built-up retort of annular units thatarc themselves built up of circle brickor the like as illustrated in Fig. 4 of the drawn T le advantages of the built-up vertical reducing chamber of the invention are many.

`The fact that the reducing chamber is suprted at its base only and not otherwise tied into the furnace structure makes possible a relatively large and long-lived chamber capable, more "especially when the individual units are made of carborundum, of -being heated to very hi h temperatures and of being shut down an started up again without beng *damaged by cracks or other faults.

The use of but one simple shape for the building up of the entire chamber makes for sim lictyand cheapness of constnucton. With such simple shapes maximum density of the tem rature-resstant material ma be obtained, t ereb giving good heat con uctivity.'- When t e built-up retort or chamber of the invention with its multiplicity of 'oints is heated up small strains, which are ound to occur, and difierences in expansion in difierent parts of the structure, due to `slightly nonuniform heating; or to sli ht differences in the density of materia s, may be relieved b flow in the cement or filler in the joints, tliereby avoiding Cracks in'the chamber as a whole, which are hardest to avoid in the heating up period of any temperature-resistant structure. Even after the structure has reached high temperatures and the bond in the joints has set, t is probable that flow can take lace in the bond more readly than it co d take lace in a true 'monolithic structure, an consequently strains will still be relieved at high temperaz tures.

While it is our preferred practice to use the simplest-forms of annular, cylindrical or standard brick shapes with plain butt joints, it may under certain circumstances be desirable to make a small departure from this practice by providing the units or shapcs with tongue and groove or equivalent joints. With such joints, it is im rtant that the grooves be nottoo dee an that good clearance be rovided therem for the tongues. It should l e borne in mind, however, that all such complications of shape tend to take away from the solidarity, trueness to shape and size and the freedom from strain and cracks oi the individual pieces. They, moreover, tend to restrict the flow in the bond, which is necessary where one piece must move with respect to another, in order to relieve strains in the assembled structure. We have found it entirely satisfactory to use nothing but plain but-t joints.

We claim:

1. An externally heated vertical reducing chamber for the reduction of zinciferous material sup orted and tied in at its lower end only and uilt up of a multiplicity ofpieces of temperature-resistant material assembled ibrto a substantially zinc-vapor-tight cham- 2. An externally heated vertical reducing chamber for the reduction of zinciferous material supported and tied in at its lower end only and built up of a multiplicity of pieccs of temperature-resistant material fittcd together with plain buttjoints into a substan tially zinc-vapor-tight chamber.

3. An externally heated vertical reducing chamber for the reduction of zinciferous ma terial supported and tied in at its lower end only and built up of a multiplicity of pieccs of temperature-resistant material fitted to gether with plain butt joints filled with a material that makes the chamber as a whole s'ubstantially zinc-vapor-tight.

4. An externally heated vertical reducing chamber for the reduction of zinciferous material supported and tied in at its lower end only"and built up of a multiplicity of super posed' annular units of temperature resistant material assembled into a substantially zine vapor-fight chamber.

5. An externally heated vertical reducing chamber for the reduction of zinciferous material supported and tied in at its lower end only and uilt upof a multiplicity of superposed annular units integrally made up of temperature-resistant material, said units be ing fitted together with plain butt joints into a substantially 'ainc-vapor-tight chamber.

6. An externally heated vertical reducing chamber for the reduction of zinciferous material supported and tied in at its lower end only and built up of a multiplicity of super posed annular units of temperature-resistant material assembled with plan butt joints nto a substantially zinc-vapor-tight cham- 7 An externally heated vertical reducing chamber for the reduction of zinciferous material supported and tied in at its lower end only and built up of a multiplicity of pieces of temperature-resistant material jointed both horizontally and vertically into a substantially zinc-vapor-tight chamber.

8. An externally heated vertical reducing chamber for the reduction of zinciferous material supported and tied in at its lower end only and built up of a multiplicity of pieces of temperature-resistant material jointed both horizontally and vertically with plain butt joints into a substantially zincvapor-fight chamber.

9. An externally heated vertical reducing chamber for the reduction of zinciferous material supported and tied in at its lower end only and built up of a multiplicity of superposed annular units of temperature-resistant material assembled into a substantially zinc-vapor-tight chamber, each of said annular units being made up of a plurality of regular shaped pieces.

10. An externally heated vertical reducing chamber for the reduction of zinciferous material built up of a multiplicity of superposed annular units of temperature-resistant material assembled into a substantially zincvapor-tight chamber, each of said annular units being made up of a plurality of circle brick, said chamber being supported at its bottom but otherwise free from attachments and bindings that interfere with its unham pered expansion and contraction.

11. An externally heated vertical reducing chamber for the reduction of zinciferous material supported and tied in at its lower end only and built up of a multiplicity of superposed rings of temperature-resistant material assembled into a substantially zincvapor-tight cylindrical chamber, each of said rings being made up of a plurality of circle brick.

12. An externally heated vertical reducing chamber for the reduction of zinciferous ma terial supported and tied in at its lower end only and built up of a multiplicity of superposed annular units of temperature-resistant material assembled into a substantially zincvapor-tight chamber, each of said annular units being made up of a plurality of reguexceeding one-sixteenth of an inch in thickness.

13. The method of making a built-up vertical retort for the reduction of zinciferous material which comprises assembling a plurality of substantially standard brick shapes into an annular unit with filled vertical joints, reducing and compressing the vertical joints between the individual brick shapes by encircling and holding compressing means, and laying said assembled annular units one upon another with filled horizontal joints while maintaining the encircling 'and holding compressing means for each unit until the weight of the superposed structure is suflicient to hold the individual brick shapes in position. r

14. The method of making a built-up vertical retort for the reduction of zinciferous material which comprises assembling a plurality of pieces of temperature-resistant material into an annular unit with filled vertical joints, redu'cing and compressing the vertical joints between the individual pieces, and superposing a multiplicity of said assembled annular units with filled horizontal joints while maintaining the vertical joints of each unit under compressiom 15. The method of making a built-up vertical retort for the reduction of zinciferous material which comprises assemblin a plurality of circle brick into an annu ar unit with filled vertical j oints, reducing and compressing the vertical joints between the individual brick, and laying said assembled annular units one upon another with filled horizontal joints while maintaining the vertical joints of each unit under compression.

16. The method of making a built-u vertical retort for the reduction of `zinci erous material which comprises assembling a plurality of circle brick into .an annular unit with filled vertical joints, reducing and compressing the vertical joints between the indil vidual brick by encircling and holding compressing means, and layng said assembled annular units one upon another with filled horizontal joints while maintaining the encircling and holding compressing mea'ns for each unit until the weight of the superposed structure is sufiicient to hold the individual brick in position,

In testimony whereof we afix our signatures. i i I FRANK G. BREYER. EARL H. BUNCE. 

